1. Field of Invention
This invention relates to fluid pumps and motors, specifically for converting energy into or from fluid motion. At least one of these pumps or motors can be combined with other components to create a heat engine such as a gas turbine.
2. Background of the Invention
Many designs have been conceived for pumping fluids. Piston pumps, screw pumps, scroll pumps, centrifugal pumps and axial flow turbines are a few of the common pumps used in industry today. Each has advantages and disadvantages over other designs. For example, single stage devices are often cheaper to manufacture but have limitation on maximum pressure drops across the pump. An example of this is the piston air compressor which is a positive displacement pump. Axial flow turbines are commonly used in large industrial devices such as jet engines. In a jet engine, the compressor is often a multistage axial flow turbine which is followed by another axial flow turbine to extract work from burning gasses. The multistage axial flow turbine represents a high efficiency method of converting energy to and from moving fluids. They are however, extremely expensive to manufacture and have complex flow losses. Some such losses are, flow over the ends of the blades. The design and manufacture of axial flow blades is complex and often expensive due to the three dimensional nature of the blades and stages. Blades generally have a complex, varying cross section across their length and require expensive manufacturing processes. Centrifugal turbines, on the other hand, can be used effectively for high flow applications but suffer efficiency losses due to being configured as single stage devices. Centrifugal turbines often include expensive impellers due to their complex three dimensional nature. There is an efficiency limit for the pressure drop across a blade or stage, often making multistage pumps and motors desirable. This however, increases the cost of manufacture and maintenance.
Since the early 20th century, turbines for extracting power from flowing fluids, such as steam, have been studied and implemented. Several such designs were characterized by turbines with long shafts, on which, disks were mounted (rotor section). On each disk, circular arrays of blades or vanes were mounted. A housing, supported the shaft with its “rotor” plates. The housing also supported circular arrays of stator blades. The fluid would flow in one end of the housing and follow a circuitous path from the inside to the outside of the disks, through the rotor and stator blades. Once the fluid reached the outside of the disk, the housing would route the fluid back toward the center where the flow pattern would repeat until the fluid was expelled out the other end of the housing. This design proved quite expensive and relatively inefficient in part, because of the tortuous path the fluid was required to flow through and large variation in swept area by each stage. There were many frictional losses, including over the blade tips. These designs eventually gave way to efficient axial flow designs.